1. Field of the Invention
This invention generally relates to a new and improved ignition system and control system for automatically, efficiently and economically igniting, combusting and controlling the temperature of a heating furnace or stove which utilizes pelletized and similar fuels.
2. Description of the Prior Art
For the years that pelletized or fragmented fuel has been combusted in independent, space-heating residential furnaces, there have not been sufficient means employed or developed which provide an automatic means for igniting and controlling the temperature of the furnace and which efficiently and economically combust pelletized or fragmented fuel of differing heating capacities. In addition to the frequent human intervention and frequent maintenance requirements of prior art, the prior art systems employed in the industry result in unacceptable temperature variation in the space to be heated.
Conventional pelletized-fuel furnaces frequently require human intervention of some sort to ignite the fuel add thereby initiate the combustion process, and also require human intervention to stop or reduce the supply of heat to the area to be heated once the desired temperature is reached. Once ignition has occurred and once the desired temperature in the area to be heated has been reached, conventional pelletized-fuel furnaces and prior ar generally keep providing heat until someone turns the furnace off, or to low-burn or to the pilot-light cycle. The prior art in the industry generally must maintain some form of a continual pilot light or other method to maintain partial or minimum combustion to avoid additional human intervention to reignite the furnace when additional heat is again required. The avoidance of the need to continually and manually turn the furnace to a lower burn rate or completely off and then manually re-igniting, results in other problems, namely unacceptably high maintenance and unacceptable temperature variances.
Prior art has heretofore been unable to develop an economical and automatic heating furnace which has an acceptable automatic control system, which allows sufficient control over the temperature of the room to be heated and sufficient system control means over the furnace elements and operation.
The pellet-burning furnaces and prior art employed in the industry have an unacceptably high frequency for maintenance for several reasons. The first is that, because of the nature of the ignition means and the frequent human intervention requirements, prior art attempts to reduce the human intervention requirements by maintaining a continuous pilot light or low-burn cycle, even when the space to be heated is at or above the desired temperature. When the prior art furnaces operate in the low-burn cycle for an impermissibly long period of time, the temperature of the products of combustion are not sufficient to prevent condensation from accumulating throughout the furnace, including through the heat exchanger and in the ducts carrying the products of combustion through the furnace to the environment.
Another characteristic of the continuous pilot-light or low-burn cycle is that the combustion rate is lowered commensurate with the lower temperature, resulting in the products of combustion containing carbon which has not yet been combusted, or soot, which tends to stick to the condensation and form layers on the internal surfaces. This build-up of soot decreases the overall heating efficiency by inhibiting the function of heat exchanger, clogging the air ducts and consequently alters the air flow through the furnace, in addition to requiring substantially more maintenance. The internal build-up of soot also provides a source of combustion on the internal surfaces and thereby increases the chance of a fire starting other than in the combustion chamber in the furnace.
The pelletized-fuel furnace industry has heretofore been unable to develop an automatic and continuous furnace that is a relatively simple design to allow it to be sold economically to a larger portion of the public for residential use.
The failure of the prior art to maintain sufficient temperature control and failure to use an effective automatic ignition system has resulted in the prior art's inability to maintain the area to be heated at a constant, predictable and comfortable temperature. The result causes unacceptable temperature variation in the area heated and requires excessive maintenance.
Our invention has greatly reduced the high maintenance requirement to an extent the prior art and the industry have not been able to achieve. Our invention utilizes an electrical-arc ignition system to eliminate the need for a continuous low-burn cycle and utilizes a system control means that maintains the desired temperature, with much less variance.
Additionally, our invention, by eliminating the situation where the furnace continues to operate when the temperature in the combustion chamber is insufficient for a complete and efficient combustion, reduces the excessive soot content of the products of combustion and reduces the maintenance requirements.
Our invention has also reduced the required maintenance by limiting the duration of the low-burn cycle to 30 minutes, which we have found to be the time when the furnace temperatures cool down to a point where condensation and consequently soot may start to accumulate in the system and require additional maintenance.
Our invention, through its electrical-arc ignition system and system control means, is an automatic ignition and automatic operation pellet-burning furnace which maintains the temperature of the area to be heated much more comfortably through its electrical-arc ignition system and use of a typical wall-mounted thermostat.
Our invention, through the configuration of the electrodes and the electrodes relative location vis-a-vis the combustion fire pot, includes safety feature whereby the electrical-arc will not ignite the fuel in the fire pot if the circulation of the combustion air is insufficient or at a standstill.
Our invention is distinguished from prior art individually or any combination thereof by providing an apparatus which eliminates the problems relating to all prior art as discussed more fully herein.